Cartoon illustrating the separator reconnection model of Wilmot-Smith & Hornig (2011). A black (white) sphere indicates the location of the upper (lower) null, the fan plane of which is seen in blue (orange) while the spines of both nulls are shown as thick black lines (due to the fan plane transparency, these lines adopt the colour of any fan planes they pass behind). Field lines are also included on each fan plane to indicate local magnetic-field orientation, coloured to match a specific plane. A separator (shown in green) links both nulls at the fan plane intersection. Time-dependent rings of magnetic flux (dot-dashed rings) induce an electric field directly along the separator (and the near vicinity); the horizontal and vertical extent of this perturbation are controlled by parameters a and l in Eq. (2).